Extreme temperatures and pressures are commonly encountered during earth drilling for oil extraction or mining purposes. Diamond, with its unsurpassed mechanical properties, can be the most effective material when properly used in a cutting element or abrasion-resistant contact element for use in earth drilling. Diamond is exceptionally hard, conducts heat away from the point of contact with the abrasive surface, and may provide other benefits in such conditions.
Diamond in a polycrystalline form has added toughness as compared to single-crystal diamond due to the random distribution of the diamond crystals, which avoids the particular planes of cleavage found in single-crystal diamond. Therefore, polycrystalline diamond (PCD) is frequently the preferred form of diamond in many drilling applications. A drill bit cutting element that utilizes PCD is commonly referred to as a polycrystalline diamond cutter (PDC). Accordingly, a drill bit incorporating PCD cutting elements may be referred to as a PDC bit.
PCD elements can be manufactured in a press by subjecting small grains of diamond and other starting materials to ultrahigh pressure and temperature conditions. One PCD manufacturing process involves forming a PCD table directly onto a substrate, such as a tungsten carbide substrate. The process involves placing a substrate, along with loose diamond grains mixed with a catalyst, into a container. Then the container in placed in in a pressure transferring cell and subjected to a high-temperature, high-pressure (HTHP) press cycle. The high temperature and pressure and catalyst cause the small diamond grains to form into an integral PCD table intimately bonded to the substrate. It is useful to remove the catalyst prior to use of the PCD, however, because properties of the catalyst have a negative effect in many applications, such as drilling. Thus, the PCD may be leached to remove the catalyst binder from all or part of the PCD. PCD from which a portion of the catalyst has been removed is referred to as leached PCD. A PCD from which substantially all catalyst has been leached is referred to as thermally stable polycrystalline diamond (TSP).